1. Field of the Invention
This invention relates in general to a position sensor for remotely sensing the position of a moving member of a mechanical apparatus. More particularly, the invention relates to a sensor and system for remotely sensing the position of a moving element of a subsea apparatus such as a blowout preventer (BOP) ram or the like.
2. Description of the Prior Art
Prior art efforts for remote sensing of moving members of mechanical apparatus have included using magnetic reed switch technology. Such technology has had only limited success for remotely measuring the position of a movable member of an apparatus for at least three reasons. First, the high failure rate of mechanical switches leads to operator distrust of the system. Second, magnetic reed technology has in practice enabled only the determination of full open or full closed positions of a movable member of a mechanical apparatus (e.g., the ram piston of a ram BOP) and then without precision. Third, and possibly most importantly, magnetic reed switch technology has lead to ambiguous display indications when the system fails completely and especially when "soft" or incomplete failures occur leading to further operator distrust of the system.
3. IDENTIFICATION OF OBJECTS OF THE INVENTION
A primary object of this invention is to provide a sensor and system which will overcome the disadvantages identified above with respect to magnetic reed switch technology in the remote sensing of the position of a movable member of a mechanical apparatus.
It is a further object of this invention to provide a measurement sensor which will not only permit continuous monitoring of the movable member of a mechanical apparatus, but will also enable detection and unambiguous display of the position of the movable member with high resolution of the position between its normal fully open or fully closed position.
It is another object of this invention to provide a position sensor and system for remotely measuring the position of the ram piston of a ram BOP by remotely sensing a visual image of an extension shaft of the ram piston and reproducing it at a remote location.
It is another object of the invention to provide a position sensor and system for a movable member of a mechanical apparatus which is immune to false positives or false negatives of the apparatus itself.
It is another object of the invention to provide a position sensor and system which presents a remote visual image of the movable member itself.